This invention relates to precipitation hardenable, nickel base alloys and more particularly to such an alloy having improved resistance to stress corrosion cracking.
An alloy has heretofore been made and sold under the designation X-750 alloy for use where a good combination of a strength and corrosion resistance is required. X-750 alloy has been produced and sold by The assignee of the present application, Carpenter Technology Corporation, having the following composition in weight percent:
______________________________________ w/o ______________________________________ Carbon 0.08 max. Manganese 0.50 max. Silicon 0.50 max. Phosphorus 0.015 max. Sulfur 0.010 max. Chromium 14.0-17.0 Molybdenum 0.26 max. Cobalt 1.0 max. Titanium 2.25-2.70 Aluminum 0.40-1.00 Columbium 0.70-1.20 Copper 0.5 max. Boron 0.003-0.008 Zirconium 0.015-0.070 Iron 5.0-9.0 Nickel Balance ______________________________________
Nickel constitutes about 70% by weight of the alloy. Included in the "Balance" are the usual incidental impurities. Here and throughout this application percent (%) means percent by weight unless otherwise indicated.
X-750 alloy has been used in the nuclear power industry for making nuclear reactor parts for service in pure water at temperatures up to about 700.degree. F. It has been found however that the resistance to intergranular stress corrosion cracking (hereinafter: stress corrosion cracking) of the X-750 alloy in such environments leaves something to be desired. Accordingly, it is a principal object of the present invention to provide an alloy having improved resistance to stress corrosion cracking and which is comparable in strength to the X-750 alloy.